The present disclosure relates to a spatial image display apparatus that displays an image in a space.
An optical system is disclosed in Japanese Unexamined Patent Application Publication No. 2008-158114 that forms an image of an object that is placed on a lower surface of a plane-symmetric imaging device, in a plane-symmetric position on an upper surface of the device, by using the device. A plurality of vertical holes having a cross-section of a square are provided in a matrix on a substrate of the plane-symmetric imaging device used in the optical system, and two mirror surfaces termed a dihedral corner reflector (DCR), which are orthogonal to each other are formed on an inner wall of each of the vertical holes. In an imaging device including a dihedral corner reflector array (DCRA) element in which a plurality of the dihedral corner reflectors are arranged on the substrate, when light emitted from the object passes through the vertical holes on the substrate, the light is reflected once at each of the two mirror surfaces constituting the dihedral corner reflector. Then, the reflected light is imaged at a position which is plane-symmetric to the substrate. As a result, the observer views a formed image (real image) that appears to be floating in a space of the upper surface of the imaging device.